When driving a motor vehicle and/or trailer combination it can be a problem for the driver to see along the side perimeter and the safe clearance area surrounding the sides of the vehicle. Front mounted headlights give illumination to the front and in some respects a wider forward field of vision beyond that of the vehicle width, at least when looking and driving forward. Rear mounted reversing lights are of little or no use to the driver in judging width, since the area immediately behind the vehicle is not visible.
Current side marker lights are again of little or no use to the driver, since they illuminate horizontally outward, rather than downward. They only give notice to other road users of some sort of vehicle presence when looking at the side of the vehicle and/or trailer.
When visibility is hampered, such as by thick fog or lashing rain, the current side marker lights are often not visible when being overtaken. Other road users have been known to go underneath an articulated trailer when in thick fog, due to the insufficient light being displayed along the side of the vehicle.
For a driver of a long vehicle is in a dark situation it is problematic to see the exact location of that vehicle or indeed anything else around it. Reference to this problem was highlighted in the 1992 heavy goods video ‘Driving Skills For Life’ Section 9D, which became the UK's Official Goods Vehicle Driving Video and was made by Creative Training. It is now 2012 and still nothing has been successfully produced to overcome this problem. Once a driver of an articulated vehicle is faced with the aforementioned dilemma, where a road might be narrow and there is no lighting, there is no way of knowing whether or not any damage is being committed by or to the side of the trailer, until the manoeuvre has taken place and the vehicle and surrounding area has been checked.